﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  179 
  

  

  Genus 
  pholidops 
  Hall 
  

  

  [Ety.: 
  (foU^, 
  a 
  scale] 
  

  

  (1859. 
  Pa^- 
  ^' 
  y- 
  3 
  489; 
  1892. 
  Pal 
  N. 
  Y. 
  V. 
  8, 
  pt 
  i, 
  p. 
  155) 
  

  

  Shells 
  small, 
  with 
  equal 
  valves, 
  patella-like 
  in 
  outline; 
  inarticulate 
  

   and 
  unattached, 
  without 
  pedicle 
  opening; 
  position 
  of 
  apex 
  variable; 
  

   edges 
  of 
  valves 
  flattened 
  where 
  they 
  meet, 
  and 
  on 
  the 
  interior 
  are 
  

   elevated 
  areas 
  for 
  attachment 
  of 
  muscles, 
  etc. 
  In 
  molds 
  of 
  the 
  in- 
  

   terior, 
  a 
  strongly 
  marked 
  impression 
  of 
  this 
  callosity 
  appears. 
  ' 
  

  

  Pholidops 
  squamiformis 
  Hall 
  (Fig. 
  82). 
  Or- 
  ^^ 
  

  

  bicula 
  ? 
  squamiformis 
  Hall 
  (1852. 
  ^ 
  ^^fc 
  

  

  Pal 
  N. 
  Y. 
  2:250, 
  pi. 
  53, 
  fig. 
  4a-b) 
  • 
  ^P 
  

  

  Distinguishing 
  characters. 
  Depressed 
  oval 
  

  

  . 
  , 
  . 
  , 
  , 
  Fig. 
  82 
  Pholidops 
  squam- 
  

  

  lorm; 
  squamous 
  concentric 
  striae, 
  most 
  marked 
  iformis 
  natural 
  size 
  and 
  

  

  enlarged 
  

  

  on 
  anterior 
  slope. 
  

  

  Found 
  near 
  the 
  middle 
  of 
  the 
  lower 
  Rochester 
  shales 
  at 
  Niagara. 
  

   Also 
  at 
  Lockport 
  (Hall). 
  

  

  Genus 
  dictyonella 
  Hall 
  

   [Ety.: 
  8iy-o(y^, 
  net] 
  

   (1867. 
  A^. 
  y. 
  state 
  cab. 
  net. 
  hist. 
  20th 
  an. 
  reft, 
  p. 
  274; 
  1893. 
  

   Pal 
  N. 
  Y. 
  V. 
  8, 
  pt 
  2, 
  p. 
  307) 
  

  

  Shell 
  subtriangular 
  in 
  outline 
  with 
  biconvex 
  valves, 
  pedicle 
  valve 
  

   having 
  a 
  broad 
  median 
  sinus, 
  and 
  brachial 
  valve 
  a 
  corresponding 
  

   fold; 
  beak 
  of 
  pedicle 
  valve 
  acute 
  and 
  arched 
  over 
  that 
  of 
  brachial 
  

   valve, 
  though 
  not 
  closely 
  appressed 
  against 
  it; 
  a 
  short, 
  triangular 
  

   deltidium 
  depressed 
  within 
  the 
  cavity 
  of 
  the 
  pedicle 
  valve 
  ; 
  teeth 
  long, 
  

   marginal 
  and 
  ridge-like 
  on 
  the 
  diverging 
  cardinal 
  slopes 
  and 
  fitting 
  

   into 
  narrow 
  marginal 
  grooves 
  on 
  the 
  brachial 
  valve; 
  brachial 
  valve 
  

   with 
  a 
  strong 
  median 
  septum. 
  Exterior 
  covered 
  by 
  a 
  coarse 
  net- 
  

   work 
  of 
  superficial 
  cells, 
  usually 
  hexagonal, 
  sometimes 
  circular 
  in 
  

   outline. 
  A 
  triangular 
  area 
  at 
  the 
  umbo 
  of 
  the 
  pedicle 
  valve 
  is 
  

   destitute 
  of 
  this 
  reticulation. 
  

  

  Dictyonella 
  corallifera 
  Hall 
  (Fig. 
  83). 
  Atrypa 
  coralli- 
  

   fera 
  Hall 
  (1852. 
  Pal 
  N. 
  F. 
  2:281, 
  pi. 
  

   58, 
  fig. 
  5a-t) 
  

  

  Distinguishing 
  characters. 
  Form 
  rhom- 
  

  

  boidal 
  to 
  subtriangular, 
  base 
  often 
  nearly 
  

  

  ^jMf 
  ^^^^ 
  straight; 
  broad 
  and 
  strong 
  sinus 
  and 
  fold; 
  

  

  reticulated 
  or 
  pitted 
  surface, 
  the 
  space 
  be- 
  

  

  Fig. 
  83 
  Dictyonella 
  corallifera 
  -vvitli 
  , 
  . 
  . 
  

  

  surface 
  enlarged 
  tWCCU 
  the 
  pltS 
  oftCU 
  pUUCtatC. 
  

  

  Found 
  in 
  the 
  Bryozoa 
  beds 
  of 
  the 
  Rochester 
  shale 
  at 
  Niagara. 
  

   Also 
  at 
  Lockport 
  (Hall). 
  

  

  